Current extent of signposting (March 2005): NR79 is signposted in the inner west of Melbourne, between Citylink and the West Gate Freeway. NR79 is also signposted in NSW between Curlwaa and Broken Hill and in QLD on the outskirts of Longreach.

National Route 79 is/was a major north-south route through Victoria, western NSW and far western Queensland. The road quality varies from 6-lane freeway in Melbourne to nothing more than a formed road near the QLD/NSW Border. It has never been fully signposted, and never will be now that most states are converting their numbering systems to the alpha-numeric style.

In the 1954 master plan for National Routes, NR79 was planned to extend from NR1 in Melbourne (then Flemington Rd) to NR66 at Longreach (now NH-A2) via the Calder and Silver City Highways, as well as several un-named roads through far-southwestern QLD. It is unclear of the exact routing between Warri Gate (QLD/NSW Border) and Longreach. A new, direct highway could have been planned but never constructed or the highway could have used existing roads through Noccundra, Eromanga, Windorah and Jundah. The final stretch into Longreach is the Thomson Developmental Road.

Signposting of this route began in 1958, with the Calder Highway getting the NR79 shield between Flemington Rd (Melbourne) and the Sturt Highway at Mildura. The initial route through Melbourne was along the original gazetted Calder Highway; Mt Alexander Road, Keilor Rd, Fullarton Rd and Old Calder Highway (Keilor).

1962 brought the northerly extension of NR79 from Mildura, through Wentworth to Broken Hill along the Silver City Highway. The extent of signposting in 1962 was about as extensive as this route ever recieved, the only major changes coming in the way of alignment changes in Melbourne and the appearance of signs in Longreach around 2002. In fact, the route is now over 500km shorter than in 1962, since NR79 was replaced through Victoria in 1997/98. The only remaining section of NR79 in Victoria is through inner-western Melbourne.

Changes in the alignment within Melbourne occurred due to the construction of the Tullamarine and Calder Freeways. Sections of the freeway were opened progressively from Flemington Rd towards Bendigo and each subsequently gained the NR79 shield. The first shift of alignment was in 1972, when the first stage of the Calder Freeway was opened between the Tullamarine Fwy at Essendon North and Keilor Rd at Niddrie. This alignment change also made use of the Tullamarine Fwy bypass of Moonee Ponds, Essendon and Strathmore. NR79 moved onto new sections of freeway to Erebus St (1974), to Green Gully Rd (1982) and to Oakbank Rd (1984). Between Melbourne and Bendigo several towns have were bypassed by NR79, including Diggers Rest (1998), Gisborne (1987) and Kyneton (1995). Other towns have since been bypassed by the M/A79, which replaced NR79 in Victoria (except for inner-western Melbourne) during 1997/98.

NR79 also had one alternative route which bypassed Bendigo to the west. This route was signposted in the early 1990's but was replaced in 1997/98 by route A790. It is known as the Calder Alternative Highway.

Current signposting of NR79 is limited to the Silver City Highway (south of Broken Hill) in NSW and a short section of road in inner-western Melbourne. NR79 was extended in 1978 from its original terminus at Flemington Bridge, south east along Flemington Rd to the roundabout with Royal Pde, Elizabeth and Peel Streets in Carlton, duplexed with Alternative 1 (part) and National Highway 8. Following the decomissioning of Alternative 1 in 1989, NR79 assumed its course from Flemington Rd to the West Gate Freeway via Harker, Curzon, Kings Streets and the Kings Way. This alignment still exists and there are no short-term plans for its decomissioning.

One proposal floated in the 1970's may have re-routed NR79 north of Tibooburra. This proposal, explained HERE, would have connected NR79 to the planned (but unsigned) alignment of NR83 near Bedourie. From a route marking perspective it would have been advantagous to the purpose of this highway to extend to NR79 shield north at least as far as Mt Isa. Regardless, this proposal was dismissed by the Commonwealth Bureau of Roads report and never constructed.